Ignition interference suppression



Aug. 28, 1934. J. M. MILLER 1,971,497

IGNITION INTERFERENCE SUPPREE S ION Filed June 10. 1935 I 6. I IINVENTOR.

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the primary current by the pressing the interference Patented Aug. 281934 UN T-so STATES PATENT OFFICE 1.911.497 IGNITION mum-amensUrrImssIoN John M. Miller,

Philadelphia, Pa, assignor to Atwater Kent Manufacturing Company,Philadolphin, Pa,

a corporation of Pennsylvania Application June It, 1933, Serial a...675,293

3 Claims. (01. 123-148) 1 My invention relates to apparatus forsupcaused by the ignition systems of motors to radioreceivers,'particularly to receivers carried by. automobiles or'aircraftand located more or less adjacent their motors.

In accordance with my invention, the interfering oscillations generatedin the ignition system are suppressed by the inclusion of radiofrequency choke coils having low direct-current resistance and lowdistributed capacity in the hightension circuit of the ignition system.My invention also resides in the features of combination, constructionand arrangement For an understanding of my invention, reference is to behad to the accompanying drawing,

in which:

Fig. 1 illustrates a typical ignition system utilizing my invention;

Fig. 2 is a sectional view on enlarged scale of one of the inductivesuppressor units;

Fig. 3 is an end sectional view taken on line 3-3 of Fig. 2.

Referring to Fig. 1, the spark-plugs 1, havingcally interrupted by thebreaker contacts 9 which a are shunted by the usual arcing. The currentfor the primary 10 of the spark coil is supplied by battery 11 which ischarged by generator 12 when the contacts of the cut-out 13 condenser Cto reduce are closed. Switch 14 is for manual closing or opening of theignition circuit in starting or stopping of the motor genericallyrepresented by the cylinder heads 15.

Thus far described; the system is a typical ig-. nition system for aninternal combustion motor, such as used in automobiles, aeroplanes, andin stationary installations. Each interruption of breaker contacts 9induces a. high-voltage inthe secondary '1 which breaks down the gap ofa spark-plug, the resulting spark igniting the charge of the associatedcylinder. The current across the spark gap not only fulfils its intendedpurpose of ignition of the cylinder mixture but also sets'up'highfrequency oscillations which seriously interfere with radio reception,particularly when the receiving apparatus is located near the ignitionsystem which is pression is sometimes improved by necessarily true whenthe receiver is carried by an automobile or aircraft. a

I have found that the noises reproduced by the receiving apparatus which'result from the interfering oscillations of the ignition system may dobe suppressed by use of the inductive units L in the high-tensioncircuit. Usually, a coil unit L is included in each of the connectionsfrom the spark-plugs 1 to its distributor contact 4; the suptheinclusion of a suppressor unit in the lead contact 6; and in some cases,a single coil unit in this position suffices. v

In all cases, the unit should be a substantially pure inductance, i. c.it should have low resistance and low distributed capacity. If theresistance of the coil is high, it will adversely affect the performanceof the motor because of the reduction of the high tension current.

Electrical disturbances arising from sparking of the generatorcommutator, of the cut-out contacts, etc., may be substantiallyeliminated by the by-pass condensers C1.

In Fig. 2 is shown an approved form of my inductive suppressor unit. Theform 15 is of bakelite, hard rubber, or the deep grooves 16 which formwinding slots for the coil which is wound, preferably from a continuousconductor, in sections or pies. When one section is wound, the conductoris passed through the slotl'! (Fig. 3) v until the coil is finished.

Winding of the coil in sections reduces the voltage per section to suchextent that there is no likelihood of breakdown by the high voltagecurrent from the spark-coil, and reduces the dis-' tributed capacity ofthe as a whole, to a minimum. A narrow, deep winding, as formed by eachof the sectio greatly increases the insulation resistance to breakdownalso reduces capacities between turns.

The coil unit shown in Fig. 2 is wound in twelve sections although it isto be understood that the umber of sections may be increased ordecreased, and in some cases afford sufficient freedom frominterference. The form may be wound, for example, with #34 double silkcovered copper wire to have a direct-current resistance of about ohmsand an inductance of the order of 10 miliihenries. The distributedcapacity is negligible. The unit, therefore, offers to distributorIf,the coil or wind- .ing has substantial distributed capacity, itseifecinto the next groove, and so on' potentials and a single sectionmay.

like having a number of a5 little opposition to flow of the high-voltagedirect current, and so does not have any appreciable effect upon themotor performance while it offers high impedance, of the order of manythousands of ohms, to the disturbing high frequency oscillations.Otherwise stated, .the unit is a substantially pure inductive, andexhibits high inductive reactance to the oscillations; the ratio of itsinductive reactance to its resistance, and the ratio of its inductivereactance to its capacitative reactance, are both very high.

The terminals 18 and 19 suitably secured to opposite ends of the formare connected to opposite ends of the coil and are suitably formed forconnection to a spark plug and its cable 3. Preferably one of them issuited for direct connection to the spark plug terminal for supportthereby.

My invention is not limited to the specific system and inductivesuppressor device described and illustrated, but is coextensive in scopewith the appended claims.

What I claim is:

1. In an ignition system for an internal combustion motor includinghigh-tension devices producing oscillations causing interference toradioreceiving apparatus, means for substantially eliminating saidoscillations without appreciably affecting the performance of said motorcomprising inductance units in series with said devices,

each unit having low direct-current resistance, low distributedcapacity, actance to said oscillations.

2. In an ignition system for an internal combustion motor includinghigh-tension devices producing oscillations causing interference toradioreceiving apparatus, means for substantially eliminating saidoscillations without appreciably affecting the performance of said motorcomprising inductance units in series with said devices, each unitcomprising a coil of high inductive reactance to said oscillations andwound in .sections to reducev the distributed capacity and to decreasethe possibility of high-voltage breakdown,

3. In an ignition system for an internal combustion motor includinghigh-tension devices producing oscillations causing interference toradio-receiving apparatus, means for substantially eliminating saidoscillations without appreciably afiecting the performance of said motorcomprising inductance units in series with said devices, each unitcomprising a core of non-magnetic material, and a plurality of seriallyconnected coil sections, said sections being spaced axiallysubstantially to reduce distributed capacity and to precludehigh-voltage breakdown.

JOHN M. .LJILLER.

and high inductive re-

